Various sensors for collecting medical information in the human body have been developed and used, herein, not only a technique for collecting information in the human body but also a technique for transmitting collected information to the outside of the human body are very important.
In a general data transmitting method, there is a communication cable method applied to an endoscope developed for observing the stomach and intestines. In the communication cable method, a cable made of a conducting wire or an optic fiber is inserted into the human body through throat of a patient. The communication cable method has high reliability and high data quality, however, a patient may suffer from severe pain during an endoscope operation.
In order to solve the above-mentioned problem, Given Imaging LTD. in Israel has developed a capsule type endoscope called M2A. When a patient swallows the capsule type endoscope like a tablet, image data in the human body photographed by a camera of the endoscope is transmitted to a receiving unit located outside the human body, and then displayed in a monitor.
However, because the M2A employs a radio wave method as a signal transmitting method, power consumption is increased, an operational time is reduced, and receiving sensitivity is deteriorated due to interference of various electric waves from the outside of the human body. In addition, because the M2A requires a radio transmitter such as a converter circuit for converting an image signal into a high frequency and an antenna for signal transmission, a volume is increased and production cost is high, and also the high frequency may be harmful to the human body. Accordingly, the present applicant has developed a human body communication system capable of transmitting data about the inside of the human body to the outside of the human body with a low frequency current by using the human body as a conductor.
In the human body communication system, an electric potential difference between transmitting electrodes that are formed on the surface of the capsule type endoscope put in the human body generates a current. As the current flows through the human body, it induces the voltage between two receiving electrodes installed on the surface of the human body, and accordingly a receiving apparatus can receive data regarding the inside of the human body.
FIG. 1 shows a human body communication system including a capsule type endoscope and two receiving electrodes. As depicted in FIG. 1, a capsule type endoscope 10 is located inside the human body 1, and a receiving apparatus 20 is located outside the human body. A transmitting electrode 11 is formed on the surface of both ends of the capsule type endoscope 10, and the receiving apparatus 20 is connected with two receiving electrodes 30 contacted to the surface of the human body. After medical information collected by the capsule type endoscope 10 is signal-processed, when electric potential difference occurs between the two transmitting electrodes 11, a current flows through the human body 2 since the two transmitting electrodes 11 are contacted with each other through body fluids and form a closed-loop. The current flowing on the surface of the human body induces a voltage between the two receiving electrodes 30 installed on the surface of the human body. The induced voltage is in proportion to the current and distance between the two receiving electrodes 30. The receiving apparatus 20 located outside the human body senses a signal transmitted from the capsule type endoscope 10 in the human body by the induced voltage.
However, when only the two receiving electrodes are used, if a direction of the current is vertical to an aligning direction of the receiving electrodes, voltage is not induced or a small amount of voltage is induced in the receiving electrodes. Accordingly, the receiving apparatus outside the human body may not receive accurately a signal transmitted from the capsule type endoscope in the human body.
In more detail, as illustrated in FIG. 1, when the capsule type endoscope 10 is located in an (A) direction, the aligning direction of the two receiving electrodes 30 is coincided with the direction of the transmitting electrode 11. In this case, a maximum current flows between the two receiving electrodes 30, so that the receiving apparatus 20 obtains good receiving sensitivity. However, when the capsule type endoscope 10 is located in a (B) direction, the aligning direction of the two receiving electrodes 30 is vertical to the direction of the transmitting electrode 11. In this case, a current does not flow between the two receiving electrodes 30, so that the receiving apparatus 20 can not receive a signal transmitted from the capsule type endoscope 10. Briefly, because the receiving electrode 30 is fixed and aligning direction of the transmitting electrode 11 is varied at any time, receiving sensitivity is varied as time elapses, a transmitted signal may be lost, and accordingly quality of receiving information is lowered.
In addition, when only the two receiving electrodes are used, position of the capsule type endoscope in the human body can not be detected, and accordingly the capsule type endoscope can not be used efficiently. For example, if we know a current position of the capsule type endoscope when the capsule type endoscope catches an abnormal symptom in the digestive organs, an accurate operation and remedy can be performed.